terça-feira, 25 de dezembro de 2012

Previous work


    4. Previous work

4a Physiological Aspects of Music Performance

Early interest in how players behave in order to operate wind instruments dates at least from the last century (Stone, 1874; Barton & Laws, 1902). Most of those studies were produced by physiologists who were mainly interested in the supposedly extreme levels of effort required, their physiological effects on circulation and respiration and on possible association to respiratory diseases (Frucht, 1937; Roos, 1936, 1938, 1940; Faulkner & Sharpey-Schafer, 1959; Singer, 1960; Akgun & Ozgonul, 1967; Watson, 1972; Gibson, 1979; Schorr-Lesnick et al., 1985; Gilbert, 1998). Part of this literature refers to pulmonary emphysema, a chronic pulmonary disease (Becker, 1911; Hävermark & Lundgren, 1957; Rejsek et al.; 1961). In this disease, there is an abnormal enlargement of the air spaces distal to the terminal bronchioles, accompanied by destruction of their walls (Snider, 1994). Yet, the claim that the playing of wind instrument might predispose to the development of pulmonary emphysema has never been confirmed (Bouhuys, 1964; Lucia, 1994). Rather, emphysema has been proved to be connected to smoking habits, to chronical respiratory disease and to genetically-related disposition (Snider, 1994). On the other hand, patients with respiratory problems who have music as an occupation are more likely to experience symptoms triggered by the demands imposed by performance. Similarly, wind players will tend to notice more clearly the physiological modifications associated with aging.

Arend Bouhuys probably contributed most importantly to the present knowledge on physiology of wind instrument playing. He studied pressure, airflow, sound power, efficiency, CO2 variations, heart rates, and other aspects (Bouhuys, 1964, 1965, 1968). Using a pneumograph he assessed qualitatively lung volume variations and also discussed some respiratory techniques, such as circular breathing (Bouhuys, 1964).

Based on the fact that blowing pressure in the observed brass instruments presented wider ranges than in woodwinds, Bouhuys hypothesised that mouth pressure control would be more important for those instruments than in any other type of winds. It must be borne in mind, however, that in brass instruments, where the lips serve as the oscillating reeds, the lip tension control is as important as the expiratory pressure. In woodwind, the embouchure, i. e. the link between the player’s mouth and the instrument (see below), is also very relevant, although it does not affect the pitch to the same critical extent as in brass instruments.

Other contributions to the physiology of wind instrument playing were given by Navrátil & Rejsek (1968), Vivona (1968), Benade (1986), among others.

4b Music Acoustics

Wind instruments have been intensely investigated in the domain of music acoustics. From the pioneering contributions of Weber (ca. 1830, as quoted by Bouasse, 1929) and Helmholtz (1863), followed by the important work of Bouasse (1929), the physics of wind instruments has attracted the attention of several generations of investigators.

With regard to reed woodwinds, particularly significant contributions were offered by Meyer (1961), Backus (1961, 1963a, 1963b, 1977), Benade (1968, 1976, 1986, 1988), Nederveen (1969), Worman (1971), Bak (1978), Plitnik & Strong (1979), Thompson (1979), Stewart & Strong (1980), Schumacher (1981), McIntyre et al. (1983), Pawlosky & Zoltowsky (1985, 1987), Gilbert (1986, 1989, 1991), Meynial (1987), Sommerfeldt & Strong (1988), Gibiat (1990), Hirschberg et al. (1990), Keefe (1990), Idogawa et al. (1993), and others.

A majority of the studies of reed instruments concern the acoustics of the clarinet, a quasi-cylindrical tube resonator excited by a simple-reed oscillator. The large concentration of studies on this instrument is probably due to the fact that the instrument possesses characteristics that are favourable from the point of view of experimental research. For example, the amplitude of vibration may be relatively small and the reed does not necessarily beat against the mouthpiece. This and the quasi-constant cross-sectional area of the tube resonator reduce complexity, particularly as compared to double reeds attached to conical tubes. In addition, the clarinet is a widespread and reasonably low-priced instrument, homogeneous in terms of design and used in many types of ensembles and styles.

The combined theoretical and experimental knowledge provided by the above-mentioned and other studies, permits simulation and prediction of instrument behaviour, at least under specific circumstances. However, many problems need still to be solved before the full system can be exhaustively described. The instruments are geometrically complex with a multitude of tonehole configurations, the reeds are neither standard, nor homogeneous, and the player’s behaviour cannot be assumed to be constant and absolutely reproducible. In addition, music requires quite fast and complex changes of the output sound. All this causes difficulties in defining parameters and initial conditions of a system of equations intended to describe, at least hypothetically, the phenomena involved. Fletcher & Rossing (1998) point out that an accurate prediction of the airflow through a wind instrument, that takes into account the effect of viscosity, necessarily requires the solution of the Navier-Stokes equations (e.g. see Yih, 1969). These are non-linear and would demand numerical methods for their solution, once the system is suitably defined.

4c Musical Pedagogy

Many pedagogical text-books for wind instruments, sometimes called "methods", often considers techniques for respiration and breathing for sound production (Quantz, 1752; Rockstro, 1890; Palmer, 1952; Rothwell, 1953, 1976; Thurston, 1956; Spencer, 1958; Stein, 1958; Sprenkle & Ledet, 1961; Bonade, 1962; Teal, 1963; Timm, 1964; Putnik, 1970; Goossens, 1977; Weait, 1979; Mazzeo, 1981; Mauk, 1986; Rehfeldt, 1994). In some cases, these sections review some basic anatomy of the respiratory apparatus, sometimes complemented by descriptions of the inspiratory and expiratory muscles, recommendations on posture during playing and on optimum inhalation strategy and instructions on how to achieve "support" and "use the diaphragm". Unfortunately, these two latter terms seem vague and used in diverging meanings among different authors. In addition, differing meanings of the same term are often used in different fields. Obviously, this lack of consensus regarding the meaning of terms will cause misunderstandings and confusion among students and colleagues.

Occasionally there is a marked discrepancy between the contents found in musical text-books and the current knowledge in respiratory physiology and mechanics; sometimes totally neglected are the great advances, achieved particularly after the end of WWII (see e.g., Rahn, 1946; Agostoni 1964, 1965, 1967; Wade, 1954; Konno and Mead, 1967, 1968; for a broad and detailed account of respiration, see Roussos, 1995). This obviously hampers interdisciplinary communication.

A professional brass instrument player and teacher, Arnold Jacobs (1915-1998), in particular, has paid major attention to respiratory aspects. Jacobs was probably the most influential wind instrument teacher in the USA and other countries, particularly among brass players. His pedagogical activities were exclusively oral, through private lessons and workshops (Stewart, 1987; Frederiksen, 1996). In his lessons, Jacobs used an ensemble of devices, developed for respiratory clinical purposes, providing visual feedback to the students regarding pulmonary pressure, air flow and lung volume. Also, he designed or adapted some equipment aiming at stimulating respiratory function in players and at increasing the degree of consciousness and training regarding muscular control. Interestingly, Jacobs used a terminology that was more pedagogically-oriented than based on physical facts. For instance, he emphasises "flow" as a keyword for playing control, as opposed to "pressure", which he deemed a negative term. This seems to be due to the psychological effect of these words. Different terms may tend to trigger different behaviours in players. Probably he did not overlook the fact that reed wind instruments and brass instruments are generally regarded as pressure-controlled systems (Benade & Gans, 1968; Elliot & Bowsher, 1982). There is also another reason for emphasising "flow". In brass instruments there is a wide range of combinations of mouth pressure and lip resistance that produce the same output level. If the player is able to use configurations requiring lower pressures, i.e., lower embouchure resistance and/or stiffness, the airflow should be maximised and the playing effort reduced (Nederveen, 1969). These general principles are likely to apply also to woodwind instruments, at least to some extent.

Music acoustics research would have the potential of contributing importantly to music pedagogy and performance. Definitions of terms based on scientific data should be easier to accept than definitions derived from experts’ introspection. Likewise, realistic ideas of anatomy and physiology have a great potential to gain wide acceptance, thus promoting interdisciplinary exchange.

©1998 by Leonardo Fuks



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